adjective

1. Of or pertaining to an omen or to omens; being or exhibiting an omen; significant.

2. Specifically, giving indication of a coming ill; being an evil omen

   “California poll support for Jerry Brown's tax increases has ominous implications for U.S. taxpayers too Los Angeles Times Headline April 25, 2011”

Synonyms: inauspicious, portentous, threatening, portentous, sinister, threatening